Process of cooling spray dried detergents



3, 1953 L. A. LEDGETT ET AL 2,657,797

PROCESS OF COOLING SPRAY DRIED DETERGENTS Filed April 23, 1948 2Sheets-Sheet 1 J LOWELL n. LEDGETT CHARLES \MDEHNE JOHN \J- MAHONEYv@#mw w 3 L. AJLEDGETT ET AL I 2,657,797

PROCESS OF COOLING SPRAY DRIED DETERGENTS Filed April 25, 1948 I 2Sheets-Sheet 2 amend om 4 LOWELL ALEDGETT q i- CHARLES w. DEANE JOHNJ.MAHONEY Patented Nov. 3; 1953 PROCESS OF cooL N SPRAY DRIED.

nu'raacuu'rs Lowell A. Ledgett, Ridgewood, and Charles W. De n S mmit,N. J., and J hn J- Mulr ney, New York, N, Y,, assignors toColgate,-Palm- JerseyCity, N. L, acorolive-Pe'et Company,

poration of Delaware ApplicationApril 23, 194 8, Serial No. 22,808

(01. aliens-i1) .5 Claims. 1

The present invention relates to an ap a for and a method of coolingspray dried organic detergents.

Spray dried organic detergents are prepar d by introducing an aqueoussolution of the detersent into the upper end or a spray tower through anatomizing device which breaks the liquid up intodroplets. During theirfall through the tower these droplets are exposed to heated air or othergas, which dries them into solid particles. The evaporation of themoisture prevents the particles from becoming heated to the temperatureof the drying gas, but in normal operation soap particles leave thetower at a temperature within the range of about 170 to 195 F. whilesynthetic detergent particles leave .at about :200 to 220 F.

Detergent particles would cake into large lumps if they were packaged atsuch an elevated temperature, The present invention has for an objectthe cooling of these hot detergent particles to a lower temperature atwhich the tendency to cake is minimized or overcome. The in vention alsocontemplates transporting and/or classifying the particlessimultaneously with the cooling thereof. Other objects and advantages ofthe invention will become apparent from the followin detaileddescription taken in conjunction with the drawings in which:

Fig. 1 is a schematic elevational view of apparatus embodying thepresent invention;

Fig. 2 is a plan view with parts broken away to reveal structuraldetails of the classifying device shown in Fig. 1;

Fig. 3 is a sectional view along the line 3--3 of Fig. 2 looking in thedirection of the arrows and; v

Fig. 4 is a fragmentary elevational view of the classifying device.

Referring now more particularly to Fig. 1, the apparatus comprises atower l of the counter current type, having a plurality of spray nozzles2 in the upper portion thereof to which theliquid detergent material ispumped through line 3 by pump 4. The bottom of the tower is in the'formof a cone 5 leading to an outlet pipe 6. The outlet pipe 6 communicateswith a pneumatic conveyor duct 1 having an air inlet 8 andleading to acyclone separator 9, where the product is separated from the air stream.A concurrent type tower may also be used, in which case tower air ratherthan atmospheric air is used in duct 1. The product leaves the separatorthrough a product outlet pipe In. The air stream is withdrawn throughexhaust line H and bag house l2 by means of a .fan 13 which places theentiresystem from the ,air inlet -8 through the has house .12 under anegative pressure.

The product leaving the cycl e separator 9 through product outlet p pel0 flows through star valve lea into asurs hopp r l4 ha ins ii feedlecI5 c mmunicati g with a pres ure ai duct 56 which loads to the bo tomofa co lin column H. The column IT has a substantially lar er iameter thanthe air duct J out duct 18 l ads from t e top of the c ling c lumn to acy lone separator .19 which has a product outlet line 20 provided with astar valve 29 and an air exhaust line =21, which .commlln With theexhaust line H,

The invention also contemplates the introdu tion of the spray driedproduct from the spray tower directly into the pr ssure air duct 16.which eliminates the air conveyor 1 and associated parts 9. Ill, l4 andI5. In such a system the tower cone to discharges the product throush anoutlet pipe to having an air lock, e. 3., a star valve 612., fortransferring the product from the lower pressure zone of the tower intothe higher pressure zone of theair duct 46.

Air under positive pressure is supplied to the duct 15,-for example, bymeans of a positive displacement blower, or compressor or turbo-com.-pressor '22. This air may be conditioned .so as to facilitate the coolinof the product. The conditioning system illustrated in the drawing oom-vprises a water .23 which is adapted to remove the heat of compression,an evaporator 24 and a mist separator 25. Liquid refrigerant is suppliedto the evaporator 24 through a liquid refrigerant line 26 and therefrigerant after evaporation in the evaporator 24 is withdrawn througha vapor line 2?! to aoompressor 28 drivon by a motor 23. The compressedvapor flows through a condenser-34 which is provided with a water inletpipe 32 and a water outlet pipe 13.

The cooled or partially cooled product from the separator "is introducedinto a classifier 34. The invention also contemplates introduction ofpartially cooled product from the separattn- 8 directly into classifier3!. Referring now more particularly to figs. 2, 3 and 4, it will be seenh h slassifl m s s a bed 35 o w ch a framework is mounted i bear n s .31at one nd and in a eccentric -3 e Psa mo i at the other end which is ata higher level. o n ed e th irem we t 36 .5 a snowmen 4.0 .ea about? msh ne bot m screen a st about 450 mes B low he bottemse e n s a .gi-ustvchut 4,2 and above the top screen u op m ll 53. thus enclosing thewithin a The chamber within the classifier communicates withthe exhaust.svsiqa 1i throne-ha plu- 3 rality of suction ducts 44 in the top wall43, a manifold 45 and a suction line 46.

Air may be introduced into the space between the screens through aconditioning air system comprising an air intake 41 in which are mountedevaporators 48. Liquid refrigerant flows into evaporators 48 throughline 49 and the evaporated refrigerant returns through vapor line 50.The air stream, after passing over the evaporators 48, is divided andflows through two branch lines which lead to manifolds 52 on each sideof the classifier. A plurality ofair ducts 53 run from each manifoldthrough the respec tive side walls of the classifier into the spacebetween the screens 4| and 4i as shown in Fig. 3. The classifier isprovided with a tailings outlet 54 for the oversized particles, aproduct outlet 55 for the particles within the desired size range and afines outlet 56 for the particles which are of smaller size thandesired. All of the ducts which connect to the classifier are providedwith flexible connectors 51 to prevent the vibration of the framework 36from traveling into the fixed lines.

The fines collected in the bag house l2 are returned for reprocessing bymeans of a conveyor belt 58. A similar belt (not shown) may be providedat the fines outlet 55 and the tailings outlet 54. The productdischarged from line 55 may go directly to packaging apparatus.

In the operation of the apparatus, the hot spray dried product which isdischarged from the tower I may be partially cooled by contact withambient air in the air conveyor system using an induced draft fan toproduce a rapidly moving stream of air which will entrain and convey theparticles by reason of the velocity alone. A satisfactory velocity forthis purpose lies within the range of about to 70 feet per second. Theperiod of contact between the air and the hot particles is limited to afew seconds by the useful length of the duct employed, but within thattime the particles may be cooled to 125 F., or somewhat lower dependingupon the temperature and humidity of the ambient air. A majordisadvantage of an air conveying system such as that illustrated in I,8, 9, l0 and ll, 12 and I3 of Fig. 1 is that if the product is cooledtherein to a safe packaging temperature it becomes sufficiently brittleto break up and produce excessive amounts of fines under the relativelyhigh impact to which it is necessarily subjected in going around bendsin the system and in the separator 9. This disadvantage is avoided inthe practice of the present invention by only partially cooling withconveying air, or preferably avoiding its use entirely, and cooling tofinal packaging temperature or thereabouts in a positive air deliverylow velocity system, e. g., a system embodying the principles of thatshown at I6, l1, l8, I9, 20, 22, 23, 24 and 25 of Fig. 1

The system utilizing the column or tower 11 has great merit even wherecooling is merely an incident to conveying of frangible particles. Inthis system the air stream has sufficient area in cross section that therate of air flow, as computed on the empty tower or duct section, isvery materially less than is operable for an airconveying system.Instead of carrying the detergent particles along by entrainment in anair stream moving at a substantially higher speed than the highestterminal velocity (i. e., the maximum velocity attained by a freelyfalling particles in still air) of the particles, the air fluidizes themass and apparently either operates like an air lift pump or operates byvirtue of pressure differentials sufficient to cause low velocity flowof the fluidized mass or perhaps functions partially in both ways. Thelower velocity of the air stream has the advantage not only of reducingthe breakage of the particles but also of prolonging the time of contactso that the cooling effect of the air is utilized more efficiently.Satisfactory results have been obtained with a system such as thatillustrated in Fig. l, where the air velocity in the cooling column I!falls within the range of about 3 to 16 feet per second. Lower andhigher velocities may be used if desired, a practical minimum beingabout 0.25 feet per second, and the maximum being less than that atwhich a substantial proportion of the particles become air conveyed. Asafe practical maximum is about 25 feet per second.

It is essential to the satisfactory operation of the lower velocitycooling system that means be provided which will build up a steeppressure gradient behind the mass of particles being treated. As thevelocity is lower than that used in air conveying, particles may depositin various portions of the system in such quantities that air pressurefar in excess of that obtainable by suction alone may be required tostart the particles moving again. In the positive air delivery systemutilizing a positive displacement blower, for example, the necessarypressure develops automatically as the blower continues to operate.

The compression of the air by a positive displacement blower results ina temperature rise due to the heat of compression. This heat is readilyremoved by a water cooled heat exchanger. When this compressed airexpands again to atmospheric or subatmospheric pressure, it exerts acooling effect upon the particles with which it is in contact in thetower [1. Under certain atmospheric conditions this may be sufficientconditioning for the treating air, but under conditions of hightemperature and high humidity it is often necessary to supply additionalartificial cooling which also dehumidifies that air. The evaporator 24is provided for this purpose and it is preferred to operate with thetemperature of the heat exchange surface just above freezing so that thecoils do not have to be defrosted. As the air becomes saturated withmoisture upon cooling to lower temperatures, the excess precipitates asdroplets on the cooling coils from which it can be readily drawn on. Anydroplets which are entrained in the air stream can be removed by anyconvenient means such as the mist separator 25.

Additional cooling may be accomplished in the classifier 34 using eitherambient or conditioned air, depending upon atmospheric conditions. Inthe process of the present invention in which the particles beingclassified are passed generally downward through the classifier screens,the cooling air is introduced transversely into the stream of fallingparticles above the bottom screen and turns upward through the upperscreen into the exhaust system. The rate of flow of the cooling air ispreferably such that most of the fines do not become air borne but passthrough the lower screens into the dust chute 42.

The following examples will illustrate the flexibility and mode ofoperation of the present invention.

Example I Spray dried soap is produced in tower l at a rate of about12,200 pounds per hour from which it is discharged at a temperature ofabout 208 F.

It is picked up in a stream of ambient air at about 69 F. (wet bulb 66F.) flowing through the air conveyor at about 73 feet per second. Thesoap which is separated from the air stream in cyclone separator 9 flowsthrough parts I0, lila, 14 and I5 into the duct I6 and cooling tower I!at a temperature of about 116 F. Here it comes in contact withrefrigerated air at a temperature of about 54 and a relative humidity of94%. This air has a velocity in the column of about 5 feet per second(computed on the basis of an empty tower). The soap leaves tower IT at atemperature of about 91 F. and with a loss of about 0.6% moisture. Itpasses through the classifier where tailings and fines are removedwithout blowing additional air into contact with the soap. The packagedproduct has no tendency to cake during storage.

Example II Spray dried soap is passed at a rate of about 13,000 pOundsper hour and at a temperature of about 122 F. into the cooling column.The ambient air, which has a temperature of 95 F. and a relativehumidity of 60%, is cooled to about 74 F. for introduction into thecooling column and the classifier. The soap is cooled to about 105 F. inthe cooling column by blowing the cooled air through it at a velocity ofabout 15 feet per second. Further cooling to about 90 F. is effected inthe classifier by blowing the cooled air into the space between thescreens at a rate of about 70 cubic feet per second. The packagedproduct remains free flowing on storage.

Although the invention has been described and illustrated in connectionwith specific illustrations of apparatus and process conditions,modifications and variations within the scope of the appended claims arecontemplated.

What is claimed is:

1. The process which comprises introducing hot spray-dried organicdetergent particles through an air look into a cooling system andfeeding them to the bottom of a mass of such particles, passing coolingair under positive delivery upwardly through said mass of particles insaid system at a velocity less than feet per second, removing cooleddetergent particles from the upper portion of said mass, conveying saidremoved particles to an air separating device, and separating saidparticles from said air in said separating device.

2. The process of cooling spray-dried organic detergent particles whichcomprises discharging the particles from a spray tower into a current ofambient air moving at avelocity of about feet to 70 feet per second inan upward direction, separating the particles from the air after a fewseconds contact, introducing the particles through an air lock into acooling system and feeding them to the bottom of a mass of suchparticles, passing cooling air under positive delivery upwardly throughsaid mass of particles in said system at a velocity less than 25 feetper second, removing cooled detergent particles from the upper portionof said mass, conveying said removed particles to an air separatingdevice, and separating said particles from said air in said separatingdevice.

3. The process which comprises introducing spray dried organic detergentparticles from a spray tower through an air lock into a cooling systemand feeding them to the bottom of a mass of such particles, passing airunder positive delivery upwardly through said mass of particles in saidsystem at a velocity less than 25 feet per second, removing detergentparticles from the upper portion of said mass, conveying said removedparticles to an air separating device, and separating said particlesfrom said air in said separating device.

4. The process which comprises introducing spray dried detergentparticles at a temperature too high for packaging through an air lookinto a cooling system, partially cooling said spray dried detergentparticles by blowing cooling air under positive delivery upwardlythrough a mass of said particles in said system at a velocity less than25 feet per second, continuously adding hot particles at the bottom ofsaid mass, continuously removing partially cooled particles from the topof said mass, and classifying the removed particles into product,tailings and fines while blowing additional cooling air transverselyinto and upwardly through a stream of falling particles to completecooling them to the desired temperature.

5. The process of cooling spray dried organic detergent particles whichcomprises introducing particles discharged from a spray tower and whilestill at a temperature too high for packaging into a current of ambientair moving at a velocity of about 30 feet to 70 feet per second in anupward direction, separating the particles from the air after a fewseconds contact, passing the particles downwardly through a plurality ofsloping classifying screens, passing streams of cooling air fromopposite sides transversely into the stream of particles above thebottom screen and withdrawing the air upwardly through the upper screen.

LOWELL A. LEDGETT. CHARLES W. DEANE. JOHN J. MAHONEY.

References Cited in the file of this patent UNITED STATES PATENTS NameDate Frisby Sept. 5, 1871 Herr Aug. 5, 1873 Girvan June 25, 1889Parkinson Dec. 16, 1889 Pfofi Nov. 7, 1899 Stanley Feb. 18, 1902 TrumpJan. 5, 1904 Busch Aug. 11, 1914 Wegner Oct. 1, 1918 Fowler Aug. 15,1922 Schwantes Apr. 20, 1926 Peterson Apr. 28, 1931 Hutton Aug. 28, 1934Smith June 1, 1937 Pehrson et a1. May 17, 1938 Ahlmann Nov. 5, 1940Arnold Dec. 16, 1941 Reinders-Folmer Apr. 21, 1942 Smith June 1, 1943Arnold Nov. 21, 1944 Mojonnier Oct. 23, 1945 Folmer Oct. 22, 1946 McGeeJuly 27, 1948 Whitman Mar. 21, 1950 Sartorius Mar. 6, 1951 FOREIGNPATENTS Country Date Great Britain Mar. 9, 1929 Number Number

